JPH07295724A - Tablet - Google Patents

Abstract

PURPOSE:To suppress the influence of noises emitted from a hand when the hand is brought close to the input face of the tablet or touches it. CONSTITUTION:There is a conductor 22 near a table input face 20 on a case 21, a hand 30 having a pen 43 touches the conductor 22 in an operating state, and the hand 30 and the conductor 22 are conducted. The conductor 22 is electrically connected to the reference potential of a circuit system 42 of the tablet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tablet for inputting information on an information processing device.

[0002]

2. Description of the Related Art Various position detecting methods already exist for a tablet in which an operator specifies a position on an input surface with a pointing tool (finger, pen, etc.) and detects the specified position. Below are examples of two methods.

Tablets using a resistance film (resistive film type tablets) are disclosed in JP-A-56-4885 and JP-A-59.
There is one disclosed in a publication such as -85584. 14
Shows an example of the method of detecting the position of the resistive film method,
The resistance film 81 and the resistance film 83 are formed by overlapping with a slight gap. In this case, a resistance film is formed on an insulating substrate (glass plate, resin sheet, etc.) by printing, coating, vapor deposition, etc., and the insulating substrates are superposed with an insulating spacer so that the resistance films face each other. .
Electrodes 82A and 82B are provided on both ends of the resistance film 81, and electrodes 84A and 84B are provided on the resistance film 83 at a pair of sides perpendicular to the electrodes 82A and 82B. Electrodes 82A, 82B
When a voltage is applied between the resistance film 81 and a potential gradient is formed on the resistance film 81, the resistance film 81 is pressed with a pen or a finger,
The resistance film 81 contacts the resistance film 83. At this time, the resistance film 8
The potential of the contact portion 87 of the first resistance film 83 is set to the resistance film 8
3, read by the signal measuring unit 86 through the electrode 84B,
Detect the position of one axis. To detect the position of the axis orthogonal to the position-detected axis, a voltage is applied between the electrodes 84A and 84B, a potential gradient is formed in the resistance film 83, and the potential of the contact portion between the resistance film 81 and the resistance film 83 is set. Do by reading. The coordinates of the pressed point are detected by alternately detecting the two orthogonal axes in time division.

As a position detecting method, there is also a method of using capacitive coupling between the pointing tool and the electrodes on the tablet input surface. As a method using this capacitive coupling, for example, there are those shown in Japanese Patent Laid-Open No. 60-171521 and Japanese Patent Publication No. 3-68411. The outline of one example of the capacitive coupling type tablet is shown below (see FIG. 15).

A large number of detection electrodes 92X for detecting the position in the X-axis direction and a plurality of detection electrodes 92Y for detecting the position in the Y-axis direction are arranged in parallel on the input surface 91. Usually, these electrodes are provided on one or two insulating substrates, and the detection electrodes 92X and 92Y are vertically displaced (perpendicular to the paper surface). Detection electrode 92
Switches 93X and 93Y are connected to X and 92Y, respectively, and the electrodes 92X and 92Y are connected to the signal measuring unit 98, respectively.
It can be selectively connected to.

A pen 96 which is a pointing device for pointing a position is connected to a signal source 97, and the pen 96 and the detection electrode 92 are connected.
By capacitively coupling X and 92Y, the signal source 9
The signal generated in 7 is measured by the signal measuring unit 98 via the detection electrodes 92X and 92Y. The switches 93X and 93Y sequentially select one or a plurality of the electrodes 92X and 92Y, and sequentially measure the signals received by the corresponding electrodes by the signal measuring unit 98 in the subsequent stage. Based on the principle that the intensity of the detection signal changes depending on the distance between the pen 96 and the electrode for measurement, the pen 9 is calculated from the values sequentially measured by the signal measuring unit 98.
6 positions can be determined.

[0007]

In order to input the position of the tablet, it is necessary to bring the finger itself, which is the pointing tool, or the hand holding the pen into contact with or approach the tablet input surface. At this time, the human body plays the role of a kind of antenna, picks up radio waves flying around and noise radiated from electronic devices such as commercial power supplies, lighting fixtures, TVs, computers, etc. It is included in the tablet position detection operation. For example, in the example of the resistance film method of FIG. 14, when the resistance film 81 is pressed by an indicator (finger, pen, etc.), noise from the finger or hand is superimposed on the original potential of the contact portion 87 at the pressing point. An error occurs in the measurement value of the signal measuring unit 86, that is, an error in the detection position occurs. Also in the example of the capacitive coupling method shown in FIG.
An error occurs in the value measured by the signal measuring unit 98 when received by 2X or 92Y. Therefore, the position calculated by the calculation also has an error. Such a problem also occurs in tablets other than the method exemplified here.

The present invention is intended to solve such a problem, and an object thereof is to provide a tablet capable of performing stable position detecting operation with a small position detecting error by reducing the influence of noise emitted from the hand. There is.

[0009]

The tablet of the present invention comprises:
A conductor electrically connected to a reference potential of a circuit system of the tablet is provided on the case of the tablet around the input surface of the tablet.

Further, a conductive layer electrically connected to the reference potential of the circuit system of the tablet is formed outside the effective position detection range of the tablet on the substrate constituting the input surface of the tablet. .

Further, the present invention is characterized in that an operation key is provided, and a conductor electrically connected to a reference potential of a circuit system of the tablet is provided at an operation portion of the operation key.

Further, the present invention is characterized in that an operation key is provided, and a conductor electrically connected to a reference potential of a circuit system of the tablet is provided on a case of the tablet near the operator side of the operation key.

Further, in a tablet used for a portable device, a conductor electrically connected to a reference potential of a circuit system of the tablet is provided in a portion held by an operator's hand of a case including the tablet. Characterize.

Further, in a tablet having an indicator connected to the main body by a cord, a conductor electrically connected to a reference potential of a circuit system of the tablet is provided at a portion of the indicator held by a hand. Characterize.

[0015]

【Example】

(Example 1) An example of the present invention mainly relating to claim 1 will be described below. Here, an example of a capacitive coupling type tablet having a cordless type pen is shown.

FIG. 1 is a diagram showing the configuration of this embodiment. The signal detection unit 4 of the tablet is provided under the input surface 20 of the tablet.
0, and the signal detection unit 40 receives a signal generated by the pen 43 having a power supply and an oscillation circuit inside. Specifically, the signal detection section 40 has the configuration of the detection electrodes 92X and 92Y in FIG. The signal received by the signal detecting section 40 is measured by the signal measuring section 41. The specific position detection operation of the tablet is the same as the conventional one, and the description thereof is omitted here. on the other hand,
A conductor 22 is provided next to the tablet input surface 20 on the case 21.
So that the hand 30 holding the pen 43 touches the conductor 22 in use. The conductor 22 is electrically connected to the reference potential of the tablet circuit system 42.

FIG. 2 is a diagram showing the structure of a specific tablet. Here, the signal detection unit 40 in FIG. 1 corresponds to the detection electrodes 92X and 92Y, the signal measurement unit 41 corresponds to the amplifier 54 to the AD converter 52, and the reference potential of the circuit system 42 of the tablet is set to the reference potential 50. Correspond. The pen 43 has a signal source 97 inside and generates an AC signal. When the pen 43 is brought close to the tablet input surface 20,
Electrodes 92 on the pen tip of the third and the tablet input surface 20.
It is capacitively coupled to X and 92Y. Switches 93X and 93Y are attached to the electrodes 92X and 92Y, respectively, and one or a plurality of the electrodes 92X and 92Y are selected and connected to the amplifier 54 in the subsequent stage. The signal amplified by the amplifier 54 is converted into a direct current level by the detection circuit 55, the sample and hold circuit 56 fixes the direct current level, and the AD converter 52 converts it into a digital value. The amplifier 54, the detection circuit 55, the sample hold circuit 56, and the AD converter 52, which are a series of signal processing systems, are connected to the reference potential 50 as one terminal of the power supply or as a reference potential. The digital value from the AD converter 52 is C
It is sent to the PU 53 and is calculated to obtain the coordinates. The conductor 22 is connected to the reference potential 50.

FIG. 3 is a perspective view of the tablet of this embodiment. A tablet input surface 20 is provided on the upper surface of a case 21 of a device including a tablet. In addition to the tablet, the case 21 also stores a display unit such as a liquid crystal display and an information processing unit that performs data processing. The operator usually operates the tablet input surface 20 from one direction, but the front side (operator side) of the tablet input surface 20.
A conductor 22 is provided on the case 21 on the left and right sides and in the vicinity thereof, and the hand is in contact with the conductor 22 when inputting on the tablet input surface 20. For design reasons, the conductor 22 may completely surround the tablet input surface 20 or may be provided only on the front side, but the hand is in a positional relationship where the hand contacts the conductor 22 in the use state. is necessary.

When actually operating, for example, when writing a character or the like on the tablet input surface 20 with a pen as an input indicator, the hand 30 holding the pen touches only the conductor 22 or Alternatively, it contacts both the tablet input surface 20 and the conductor 22. Then, the reference potential 50 of the tablet circuit system and the hand 30 of the operator are electrically connected, and the hand 3
The noise emitted from 0 passes through the conductor 22 and has a reference potential of 50.
Be escaped to. Therefore, the noise that affects the tablet input surface 20 from the hand 30, that is, the noise of the signal received by the detection electrodes 92X and 92Y and input to the amplifier 54 is reduced, and the accuracy of the position detection of the tablet is improved.

Although the cross-sectional shape of the conductor 22 is a rectangular cross section in FIG. 1, it is not limited to this and may be a semicircular cross section, a trapezoidal cross section or the like.

When the conductor 22 is made of a metal, it is very preferable that it is a metal having excellent corrosion resistance such as stainless steel and titanium. The conductor 22 may be made of a metal or the like, and may be made of a flexible conductor such as conductive rubber or conductive sponge. As a result, the hand 30 can be brought closer to the tablet input surface 20 while being in contact with the conductor 22, so that the usability can be improved without reducing the effects of the present invention. Furthermore, by providing a metal conductor on the flexible conductor, it is possible to increase the durability as compared with the case of using only the flexible conductor.

(Embodiment 2) An embodiment of the present invention relating to claim 2 will be described below.

FIG. 4 is a perspective view of the tablet of this embodiment. A tablet input surface 20 is provided on the upper surface of a case 21 of a device including a tablet. The conductor layer 23 is provided on the input surface 20 of the tablet outside the effective position detection range, that is, in a region where the position cannot be actually detected or where the position need not be detected. The conductor layer 23 is electrically connected to the reference potential of the tablet circuit system. The conductor layer 23 needs to be positioned so as to be electrically connected to the operator's hand when the tablet is actually used. If the tablet is used from only one direction, the conductor layer 23 may not be partially provided on the opposite side of the operator side (front side) as shown in FIG. The substrate 25 that constitutes the tablet input surface 20 is made of an insulating material such as glass.
The conductor layer 23 is attached by vapor deposition, coating, printing or the like on the substrate 25 in the peripheral portion outside the effective position detection range of 0. In the case of a transparent tablet which is used by stacking a tablet on a display unit such as a liquid crystal display, the substrate of the tablet input surface 20 is made of glass or transparent resin, but in that case, the conductor layer 23 is a transparent electrode. It may be formed of some ITO or the like, and if the transparency does not matter because it is outside the effective input range, the conductor layer 23 may be a metal thin film. The conductor layer 23 is electrically connected to the reference potential of the tablet circuit system. The connection method between the conductor layer 23 and the reference potential is
1) A conductive material is used for a part or all of the case 21 to electrically connect the conductor layer 23 and the case 21, and the case 21 and the reference potential of the tablet circuit system.
How to connect through. 2) A method of passing through the signal detection unit 40 existing on the back side of the substrate 25 of the tablet input surface 20. and so on.

The specific structure of the tablet detection system may be the same as that of FIG. 2 in the first embodiment, and the description thereof will be omitted here.
However, the conductor 22 in FIG. 2 is replaced with the conductor layer 23 as it is.

Similar to the first embodiment, when a user holds a pen as an input indicator to write a character, the hand holding the pen contacts the conductor layer 23, and noise from the hand causes the conductor layer to come into contact. Two
It passes through 3 and escapes to the reference potential of the tablet circuit system. Therefore, noise that affects the tablet position detection is reduced, and the tablet position detection accuracy is improved.

Since the conductor layer 23 is used to electrically connect the operator's hand to the reference potential of the circuit system of the tablet, it is possible to make the structure lightweight and compact.

(Embodiment 3) An embodiment of the present invention relating to claim 3 will be described below. Here, a tablet using a resistive film method is shown as an example.

FIG. 6 is a perspective view of the tablet of this embodiment. The tablet input surface 20 is provided on the upper surface of the case 21 of the device including the tablet as in the first embodiment. A display device (not shown) is provided below the tablet input surface 20, and an arbitrary position displayed on the display device can be designated by the tablet. Tablet input surface 2
Two operation keys 24 are arranged on the upper surface of the case 21 next to 0, and a conductor 22 is attached to the surface of the operation key 24 to be pressed by a finger, which is a reference potential of the tablet circuit system. Is electrically connected to.

FIG. 7 is a diagram showing the structure of the detection system of the tablet. Electrodes 82 are provided on a pair of opposing sides of the resistance film 81.
A and 82B are provided, and the resistance film 83 is provided with electrodes 84A and 84B on a pair of sides that are orthogonal to the sides of the resistance film 81 on which the electrodes 82A and 82B are provided. Each of the electrodes 82A, 82B, 84A, 84B is connected to the switch group 88, and the voltage from the voltage source 51 is applied to either end of either the resistance film 81 or the resistance film 83. For example, in FIG. 7, the switch group 88 is tilted upward, the voltage source 51 is connected to the electrodes 82A and 82B, and a potential gradient is applied to the resistance film 81. here,
One pole (negative pole in this example) of the voltage source 51 has a reference potential 50.
It is connected to the. On the other hand, one of the electrodes 82B and 84B is selected by the switch group 88 and connected to the AD converter 52. Switch group 8 for position detection
8 cooperates to connect the AD converter 52 to the electrode 84B of the resistance film 83 different from the resistance film 81 connected to the voltage source 51 in FIG. The AD converter 52 has reference inputs ref0 and ref1, and is input to the analog input Ain with a full scale from the potential input to ref0 to the potential input to ref1 with reference to the potential input to ref0. It has the function of converting the amount of voltage into a digital value and outputting it. ref0 is connected to the reference potential 50, and ref1 is connected to the positive side of the voltage source 51. When the input surface of the tablet is pressed, the resistance film 81
The resistance film 83 locally contacts with the resistance film 83, and the potential at the contact position is input to the AD converter 52. The digital output value of the AD converter 52 is sent to the CPU 53, and the coordinates of the designated position of the tablet are calculated. The conductor 22 is connected to the reference potential 50.

With the above-mentioned configuration, it is possible to emulate a mouse which is one of position input devices for information equipment. FIG. 8 shows a usage state of the tablet of this embodiment. The right hand 32 points to the position of the tablet input surface 20. That is, it follows the operation of specifying the position on the mouse. On the other hand, the operation key 24 corresponds to an operation button on a mouse. The left hand 33 operates the operation key 24, and at the position pointed by the right hand 32, the left hand 33 operates the same function as the mouse clicking operation.

In such an operation, when the left hand 33 operates the operation key 24, the left hand 33 comes into contact with the conductor 22 attached to the operation key 24, and the noise of the human body causes the conductor 22 to contact the conductor 22. It escapes to the reference potential. As a result, the influence of noise from the right hand 32 on the tablet input surface 20 is reduced, and the accuracy of tablet position detection is improved.

In the present embodiment, the operation key 24 has been shown as an example having the same function as that of a general mouse, but the use of the operation key 24 is not limited to this example. The number of operation keys 24 is also arbitrary.

Although the resistance film method has been described in this embodiment, the present invention is not limited to the resistance film method.
The same configuration can be applied to tablets of other methods such as capacitive coupling method.

(Embodiment 4) An embodiment of the present invention relating to claim 4 will be described below.

FIG. 9 is a perspective view of the tablet of this embodiment. A tablet input surface 20 is provided on the upper surface of a case 21 of a device including a tablet. Operation keys 24 are arranged beside the tablet input surface 20 on the upper surface of the case 21. In this case, the position input operation can be performed on the tablet input surface 20 with one hand, and at the same time, the operation key 24 can be operated with the other hand. Operation key 24
A conductor 22 is attached to the case 21 on the front side of the. The conductor 22 is provided at a position where the palm of the hand when pressing the operation key 24 with a finger or the part of the wrist comes into contact. This contact position is about 5 cm from the front side of the operation key 24 to 20
The position is in the cm range, and it is necessary to provide the conductor 22 in at least a part of this range to make contact with the hand. The conductor 22 is electrically connected to the reference potential of the tablet circuit system.

The configuration of the detection system of the tablet is the same as that described in the third embodiment, as shown in FIG. 7, and the description thereof is omitted here.

Similar to the third embodiment, it can be used as a mouse emulation. Positioning is performed with one hand on the input surface 20 of the tablet. At the same time, the operation key 24 is operated with the other hand to perform the same function as the mouse clicking operation.

In order to put the hand on the conductor 22 when the operation key 24 is actually operated or when the operation key 24 is prepared to be operated, conduction is established between the hand and the conductor 22. At this time, the noise from the human body is released to the reference potential through the conductor 22, and therefore the noise that affects the tablet from the hand that performs the position pointing operation opposite to the hand that contacts the conductor 22 is reduced, and the tablet This has the effect of improving the accuracy of position detection.

It is more preferable that the portion of the conductor 22 is recessed so as to fit the shape of the palm so that the hand can be stably placed on the conductor 22. In this case, if the area of the conductor 22 is increased, the contact area between the hand and the conductor 22 is increased, and the effect of reducing noise is further enhanced.

(Embodiment 5) An embodiment of the present invention relating to claim 5 will be described below.

FIG. 10 is a perspective view of the tablet of this embodiment. This is an example of using a tablet for a portable information device that can be operated while being held by hand. A tablet input surface 20 is provided on the upper surface of a case 21 of a device including a tablet. The input operation on the tablet input surface 20 is performed with a pointing tool for pointing a position or a finger. If the tablet position detection method is a resistive film method, position indication is performed with a finger or a rod-shaped tip made of resin etc. that does not damage the tablet input surface, and it may be capacitive coupling method or electromagnetic induction method. For example, it is common to use a dedicated pen. When using the information device including the tablet with the case 21 by using the hand 30 that is different from the hand holding the pointing device for pointing the position or the hand to which the finger pointing the position belongs, the hand 3
A conductor 22 is attached to a portion that holds the case 21 at 0. The conductor 22 is connected to the reference potential of the tablet circuit system. The type of tablet detection method is not particularly limited, and for example, the capacitive coupling method illustrated in the first embodiment,
The resistance film method and the like shown in Embodiment 3 are also possible.

In actual use, the case 21 is held by the hand 30.
As long as the hand 30 is used while being held, the hand 30 and the reference potential of the tablet circuit system are always brought into conduction via the conductor 22, and noise from the human body is released to the reference potential. Therefore, when a position pointing operation is performed on the input surface 20 of the tablet, noise that affects the input surface 20 of the tablet from a hand that positions the side opposite to the hand holding the case 21 is reduced. , The position detection accuracy of the tablet is improved. The user has an effect of being able to reduce the influence of noise on the tablet by an operation that the user does not have to be aware of by holding the holding part of the information device by hand.

In the example of FIG. 10, the conductor 22 is attached to the upper surface of the case 21, but it may be attached to the holding portion on the lower surface. Further, in order to hold the case 21 easily, the portion of the conductor 22 may be recessed or formed in a handle shape. Alternatively, the case 21 itself may be formed with a depression or formed into a handle, and the hand 30
The conductor 22 may be provided in a portion that contacts with.

(Embodiment 6) Another embodiment of the present invention relating to claim 5 will be described.

FIG. 11 is a perspective view of the tablet of this embodiment. This is an example in which a tablet is used for a portable information device that can be operated with a hand as in the case of the fifth embodiment. A tablet input surface is provided on the upper surface of the case 21 of the device including the tablet. The width of the case 21 in this embodiment is at most about 10 cm, and the tablet can be operated while holding both side surfaces of the case 21 with the hands 30. Hand 3
The conductor 22 is attached to the part of the case 21 that holds the case 21 at 0, that is, the side surface of the case 21. The conductor 22 is connected to the reference potential of the tablet circuit system. In FIG. 11, the conductor 22
Is attached to both side surfaces of the case 21, but only one side surface may be provided.

In actual use, the case 21 is held by the hand 30.
As long as it is held and used by the user, the hand 30 and the reference potential of the tablet circuit system are always in a conductive state, and noise from the human body is released. Therefore, the position detection accuracy of the tablet is improved.

(Embodiment 7) An embodiment of the present invention relating to claim 6 will be described below. In the present embodiment, an example of a pen type tablet with a cord in which a pen as an indicator is connected to the main body by a cord is shown.

FIG. 12 is a view showing a pen portion of the tablet of this embodiment. A cord 44 is attached to the pen 43, and is connected to the tablet body through the cord 44. Several conductors run through the cord 44. As a method of this pen type tablet with code,
In addition to the one that emits a signal from the pen 43 and the tablet body receives and measures the signal, a signal is emitted from the tablet body,
For example, the pen 43 receives a signal, performs all or part of the signal measurement in the pen 43, and sends the result to a main body through a code. Hand 43 of pen 43
A conductor 22 is attached to a portion for holding the so as to be electrically connected to the hand 30. The conductor 22 is connected to the reference potential of the tablet circuit system through one of the conductors passing through the cord 44.

FIG. 13 shows the internal circuit configuration of the pen 43. The signal received by the pen tip 61 is input to the amplifier 62, amplified, and sent to the tablet body through the conductor 67. The power to operate the amplifier 62 is provided by a conductor 65,
It is supplied from the tablet body through 68. One of the conducting wires 68 is connected to the reference potential 60 inside the pen. The state of the switch 63 used as a pen click detection or a push button is sent to the tablet main body through a conductor 66. The conductor 22 is the reference potential 6 inside the pen.
0 is connected to the reference potential of the tablet body via the conductor 68.

When the user holds the pen 43 with his / her hand 30 to input data on the tablet, the conductor 22 attached to the portion holding the pen 43 always keeps the hand 30 and the reference potential of the tablet circuit system in a conductive state. Become. Therefore, noise from the human body is released, and the position detection accuracy of the tablet is improved.

A metal may be used for the conductor 22, but a conductor having flexibility such as conductive rubber is more preferable because it is easy to hold by hand and excellent in operability.

[0052]

As described above, according to the present invention,
The hand of the operator of the tablet and the reference potential of the circuit system of the tablet are electrically connected to each other, and the conduction to the reference potential is performed without the operator being particularly aware.
Therefore, when actually operating the tablet, for example, when holding a pen as an input indicator in the hand to write a character or the like on the tablet input surface, or when directly indicating a position with a finger or the like, conventionally The noise emitted from the hand indicating the position can be released to the reference potential, the noise affecting the tablet from the hand is reduced, and the accuracy of the position detection of the tablet is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a tablet of the present invention.

FIG. 2 is a diagram showing a configuration of a detection system of the tablet according to the first embodiment of the present invention.

FIG. 3 is a perspective view of the tablet according to the first embodiment of the present invention.

FIG. 4 is a perspective view of a tablet according to a second embodiment of the present invention.

5 is a cross-sectional view of a portion of the tablet input surface 20 of FIG.

FIG. 6 is a perspective view of a tablet according to a third embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a detection system of the tablet of Example 3.

FIG. 8 is a diagram showing a usage state of the tablet of Example 3;

FIG. 9 is a perspective view of a tablet according to a fourth embodiment of the present invention.

FIG. 10 is a perspective view of a tablet according to a fifth embodiment of the present invention.

FIG. 11 is a perspective view of a tablet according to a sixth embodiment of the present invention.

FIG. 12 is a diagram showing a tablet pen according to a seventh embodiment of the present invention.

FIG. 13 is a diagram showing a circuit configuration inside a pen of Example 7.

FIG. 14 is a diagram showing a configuration of a resistance film type tablet of a conventional example.

FIG. 15 is a diagram showing a configuration of a conventional capacitive coupling type tablet.

[Explanation of symbols]

 20 ... Tablet input surface 21 ... Case 22 ... Conductor 23 ... Conductor layer 24 ... Operation key 25 ... Tablet input surface substrate 30 ... Hand 32 ... Right hand 33 ... Left hand 40 ... Signal detection unit 41 ... Signal measuring unit 42 ... Tablet circuit System 43 ... Pen 44 ... Code 50 ... Reference potential 51 ... Voltage source 52 ... AD converter 53 ... CPU 54 ... Amplifier 55 ... Detection circuit 56 ... Sample hold circuit 60 ... Reference potential 61 ... Pen tip 62 ... Amplifier 65-68 ... Conductive wires 81, 83 ... Resistive films 82A, 82B, 84A, 84B ... Electrodes 88 ... Switches 92X, 92Y ... Detection electrodes

Claims (6)

[Claims] 1. A conductor electrically connected to a reference potential of a tablet circuit system is provided around the input surface of the tablet.
A tablet provided on the case of the tablet. 2. A conductive layer electrically connected to a reference potential of a circuit system of the tablet is formed on a substrate constituting an input surface of the tablet, outside the effective position detection range of the tablet. Tablet. 3. A tablet comprising an operation key, wherein a conductor electrically connected to a reference potential of a tablet circuit system is provided at an operation portion of the operation key. 4. A tablet comprising an operation key, wherein a conductor electrically connected to a reference potential of a circuit system of the tablet is provided on a case of the tablet near the operator side of the operation key. 5. A tablet used for a portable device, wherein a conductor that is electrically connected to a reference potential of a circuit system of the tablet is provided in a portion of the case including the tablet that is held by an operator's hand. Characteristic tablet. 6. A tablet having an indicator connected to the main body by a cord, wherein a conductor electrically connected to a reference potential of a circuit system of the tablet is provided in a portion of the indicator held by a hand. Characteristic tablet.